Patent GB-812057-A (GB)
Title: Variable ratio photoelectric copy reproducing machine
IPC: B41C1/04
Filed: 1955-04-25
Abstract: 812,057. Local copying by scanning. FAIRCHILD CAMERA & INSTRUMENT CORPORATION. April 25, 1955 [May 10, 1954], No. 11844/55. Class 40 (3). In a photo-electric image-reproducing ma. chine in which a copy on a support is scanned in one direction at a uniform velocity by an oscillatable optical element in combination with a light source and a photo-electric device and in a transverse direction by relative movement between the copy support and the scanning means which provides signals for a transducer to act upon a recording sheet to form a reproduction of the original copy by corresponding movement of the transducer relative to the sheet in two approximately perpendicular directions, the relative movements of the transducer and the sheet-supporting means in said perpendicular directions are controlled at adjustable ratios relative to the corresponding movements between the copy support and said scanning device. The magnitude of movement of the oscillatable optical element is adjusted symmetrically on both sides of a central position corresponding to the centre line of the copy on the support. The arrangement permits originals of varying dimensions to provide reproductions of predetermined dimensions and by using a reproducing cylinder of different dimensions, further variations of the ratio between the sizes of the original and reproduction can be obtained. In the diagrammatic arrangement, Fig. 2, the copy on a table 30 is scanned by a mirror 54 oscillated by mechanism 34 driven through a clutch 50 from the shaft 361 of a transmission arrangement 26 which has an output shaft 45 effecting the movement of the copy support 30. An output shaft 36 rotates a receiving drum 22 and a further shaft 38 effects the transverse movement of an engraving head 16., The speed of the head 16 may be adjusted to vary the fineness, and consequently one of the dimensions of the reproduction and the screen frequency is controlled by a tone drum 58 having a number of circumferential tracks which can be selectively operated to produce different pulse frequencies applied to the modulator 62. The clutch 50 may be operated to disconnect the scanning mechanism 34 so that a predetermined area on the copy may be reproduced for examination or adjustment purposes. Reproducing arrangement.-The driving motor 64, Fig. 3, which may operate at two predetermined speeds, rotates through gears 68 and 70, Fig. 4, the shaft 36 carrying the receiving drum 22. A spiral gear 72 engages gears 74, 76 to drive gears 86, 88 which selectively drive shaft 38 under control of clutches 94 operated by a knob 96. A clamp 44 on a straight portion of a belt 40 passing round a pulley 98 on the shaft 38 traverses the engraving head 18 relative to the drum 22. A gear 104 on the shaft 66 of the motor 64 rotates a shaft 106 carrying a disc 108 with a set of balls 110 engaging a cylinder 112 which through gears 120, 122, 124, 126 drives a shaft 45 carrying a pulley 46 which through a metal band 48 and clamp 142 advances the support 30 for the copy being scanned. The rate at which the support 30 is moved may be varied by adjusting the transmission ratio between the disc 108 and cylinder 112, the position of the balls on the disc 108 being changed by an adjusting spindle 114. The recording may be effected by indenting, removing parts of surface by a heated stylus or by modulated light. In the latter case the sheet carried by the cylinder 22 may be a plastic which is locally hardened by a light beam and the recorded plate subjected to a photoengraving process to produce a direct printing element. Transmitting arrangement.-The tone drum 58, Fig. 3, secured to the shaft 36<SP>1</SP> carries three separate magnetic tracks 144 arranged to produce three different tone frequencies. The shaft 52 controlling the oscillation of the scanning mirror 54 is connected to the shaft 361 by the clutch 50 and carries a cam 168 operating a roller 170 which is constrained to move up and down by parallel linkages 174, 176, 178. The roller 170 engages the arm of a pivoted yoke member 188 having arms 190, 192 engaging members 196, 198 on a shaft 200 mounted in parallel links 202, 204 connected by links 206, 208 to a carriage 214. The shaft 210 carries a block 220 engaging a lever 222 carrying a sector 226 linked by an inextensible band 228 to a sector 230 on a shaft 232 carrying the mirror 54. The amplitude of movement of the mirror 54 is changed by the movement of the carriage 214 which effectively alters the fulcrum of the lever 222. The position of the carriage 214 is changed by rotating wheel 252 which through gears 246, 248 rotates the threaded shaft 216. Simultaneously with the variation of amplitude of the scanning movement, the defining aperture 352 through which the scanning beam passes before impinging on the photo-cell 56 is correspondingly varied by gears 260, 262 rotating a sleeve carrying cam operating rods connected to crank members which rotate two diaphragm members defining the aperture. When the system is operated at a different speed, the sleeve and operating cam are moved inwardly by the knob 366 so that a variation of the amplitude of the mirror movement produces a relatively larger variation of the size of the aperture 352. Compensation is made for the difference in path length of the scanning beam during its scanning transit by altering the position of the lens 266 relative to the lens 268. The lever 222 which is raised and lowered to control the oscillatory movement of the mirror 54 carries a roller 280 which at the beginning of the scanning of a line is in a raised position and is in engagement with the upper portion of a lever 282 connected to a frame member 294 which is connected. by a latch 314 and rod 316 to a rod 302. When the lever 222 and roller 280 move downwardly, the frame member 294 is moved to the left so that the rod 302 is rocked and the lens 266 is moved towards the lens 268 to a position corresponding to the central position of the scanning beam. As the lever 222 continues its downward movement, the latch 314 is disengaged and the roller 280 engages the surface of a downwardly extending lever 284 so that a frame member 298 and rod 302 are moved forwardly and the lens 266 is moved away from the lens 268 to the position in which it is held by the engagement with a fixed stop 320. During the return movement of the scanning beam and the raising of the lever 222 and roller 280 to its upper position for the commencement of the next scanning line, the roller 280 is clear of the lever 284 and latch bar 294 is held by latch 318 until the lever 222 nears its upper position. Movement of the bar 294 when released does not affect frame bar 298 on account of a pin and slot connection with a rod 328 carried by the latch bar 294. The latches 314, 318 are connected to rods 336, 338 mounted in a lever which is moved upwardly by a member rocked by an arm 334 moved longitudinally by a cam 330 on the shaft 52. The arrangement by which the mirror is rocked by the sector 226 on the shaft 224 of the lever 222 compensates approximately for the movement of the scanning beam and recording point over linear and circular paths respectively. To provide a diagonal pattern of engraved dots in lieu of the normal rectangular pattern, the output of the tone generator track in use is reversed in phase during alternate revolutions of the shaft 52 by a switch operated by a lever 164 controlled by a gear-wheel 156 rotated at half the speed of the shaft 52. Specification 692,349 is referred to.